Styrenic thermoplastic resin composition containing an aromatic pentaerythrityl diphosphate

ABSTRACT

The present invention relates to a styrenic thermoplastic resin composition, and more particularly to a styrenic thermoplastic resin composition comprising a non-halogen flame-retardant having superior flame-retarding properties and impact strength. The present invention provides a flame-retarding styrenic thermoplastic resin composition comprising a) 100 weight parts of a base resin comprising i) 10 to 50 weight parts of a rubber-modified styrenic-containing graft copolymer, ii) 5 to 20 weight parts of phenol novolac resin, and iii) 20 to 70 weight parts of a styrene-containing copolymer; and b) 5 to 20 weight parts of an aromatic phosphate. In addition, the a) base resin may further comprise iv) 10 to 40 weight parts of a thermoplastic polyurethane resin.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to a styrenic thermoplastic resincomposition, particularly to a styrenic thermoplastic resin compositioncomprising a non-halogen flame retardant having superior flame-retardingproperties and impact strength.

(b) Description of the Related Art

Rubber-modified styrene resin has superior processibility and physicalproperties. In addition, it has superior appearance and impact strengthand thus it is largely used for electric and electronic appliances andoffice appliances. When used for electric and electronic appliances andoffice appliances, a great deal of heat is produced and there is adanger of fire, and thus the resin used should have flame-retardingproperties. Therefore, many studies for imparting flame-retardingproperties to rubber-modified styrenic resin having flammable propertieshave been conducted.

As a result of many studies over a long period of time, it is known thatthe use of halogen compounds as flame retardants is the most effectivemethod to make rubber-modified styrenic resin flame retardant. Also, itis known that tetrabromobisphenol A and brominated epoxy, etc. are themost commonly used halogen containing flame-retardants, and thatantimony compounds have synergistic effects for flame-retardingproperties.

However, halogen compounds are known to produce gases corroding metallicparts during processing, and to decompose during firing to dischargetoxic gases that are noxious to the human body. Particularly, brominatedcompounds are criticized and restricted around Europe because they mayproduce environmental hormones that are noxious to the human body, suchas dioxins or furans when combustion. Antimony compounds are alsoclassified as toxic material.

Accordingly, studies of flame retardant resin compositions that do notuse halogen compounds and antimony have attracted a great deal ofattention. Because it is difficult for rubber-modified styrenic resin tohave superior flame-retarding properties if using a non-halogen flameretardant, the development of methods for blending polycarbonate andrubber-modified styrenic resins have been attempted many times. However,a blend of polycarbonate/rubber-modified styrenic resin can achieve thedesired flame retardant properties only if 70 wt % or more ofpolycarbonate is used. Also, if polycarbonate is used such a high level,advantages of rubber-modified styrenic resin cannot be utilized and itbecomes unfavorable in terms of processibility and economy.

In addition, red phosphorus or expandable graphite can be used in theresin composition in order to make rubber-modified styrenic resin flameretardant without using a polycarbonate. But, in this case, physicalproperties are inferior and only a dark colored product can be prepared.

SUMMARY OF THE INVENTION

The present invention is made in consideration of the problems of theprior art, and it is an object of the present invention to provide astyrenic thermoplastic resin composition comprising a non-halogen flameretardant having superior flame-retarding properties and impactstrength.

In order to achieve the object, the present invention provides aflame-retarding styrenic thermoplastic resin composition comprising:

-   -   a) 100 weight parts of a base resin comprising        -   i) 10 to 50 weight parts of a rubber-modified            styrene-containing graft copolymer;        -   ii) 5 to 20 weight parts of phenol novolac resin; and        -   iii) 30 to 70 weight parts of a styrene-containing            copolymer; and    -   b) 5 to 20 weight parts of an aromatic phosphate.

Preferably, the present invention provides a flame-retarding styrenicthermoplastic resin wherein the a) base resin further comprises 10 to 40weight parts of a iv) thermoplastic polyurethane resin.

DETAILED DESCRIPTION AND THE PREFERRED EMBODIMENTS

The present invention will now be explained in detail.

The present invention blends a small amount of a thermoplasticpolyurethane resin and phenol novolac resin instead of a polycarbonateso as to maintain advantages of a rubber-modified styrenic resin, anduses aromatic phosphate as a flame-retardant, thereby obtaining athermoplastic resin composition having superior physical properties offlame-retarding and impact strength.

(Rubber-Modified Styrene-Containing Graft Copolymer)

The rubber-modified styrene-containing graft copolymer used in thepresent invention is obtained by grafting a compound comprising 30 to 65weight parts of at least one of styrene, α-methylstyrene, and nuclearsubstitution styrene; and 10 to 30 weight parts of at least one ofacrylonitrile, methylmethacrylate, and butylacrylate, to 10 to 60 weightparts of rubber. Examples of the rubber include polybutadiene, astyrene-butadiene copolymer, polyisoprene, a butadiene-isoprenecopolymer, etc. The graft copolymer resin can be prepared by a commonpolymerization method, but it is preferably synthesized by masspolymerization and emulsion polymerization. Particularly,acrylonitrile/butadiene/styrene (ABS) resin wherein acrylonitrile andstyrene are grafted on butadiene rubber is preferable.

The rubber-modified styrene-containing graft copolymer comprises a baseresin together with thermoplastic polyurethane resin, astyrene-containing copolymer, and phenol novolac resin, and it is usedin an amount of 10 to 50 weight parts of the total base resin. If thecontents of the rubber-modified styrene-containing graft copolymer areless than 10 weight parts, physical properties including impact strengthdecrease, and if it exceeds 50 weight parts, processibility decreasesand rigidity and hardness become lower.

(Thermoplastic Polyurethane Resin)

The thermoplastic polyurethane resin used in the present invention is ageneral polymer produced by a polymer addition reaction of amulti-functional isocyanate and a compound having two or more hydroxylgroups. Therefore, the thermoplastic polyurethane resin may includebonds other than a urethane bond, such as urea, amide, biuret,allophanate, ether, ester, etc. bonds.

The thermoplastic polyurethane resin comprises a base resin togetherwith a rubber-modified styrene-containing graft copolymer, a styrenecontaining copolymer, and phenol novolac resin, and it is used in anamount of 10 to 40 weight parts of the total base resin. If the contentsof the thermoplastic polyurethane resin are less than 10 weight parts,flame retarding properties may decrease, and if it exceeds 40 weightparts, processibility will be decreased.

(Phenol Novolac Resin)

The phenol novolac resin used in the present invention is obtained byreacting phenols and formalin in the presence of an acidic catalyst. Ithas a structure of the following Chemical Formula 1, and it is used inan amount of 5 to 20 weight parts of the total base resin. If thecontents of the phenol novolac resin are less than 5 weight parts, itshows no flame-retarding properties, and if it exceeds 20 weight parts,processibility decreases.

(wherein X is CH₂, CH₂CH₂, CHCH₃, CO, or SO₂; each of R is independentlyor simultaneously a hydrogen atom, a halogen atom, a C₁₋₂₀ alkyl group,an aryl group, NO₂, CN, Si, or a hydroxyl group; and n is an integer of1 or more, showing degree of polymerization)

(Styrene-Containing Copolymer)

The styrene-containing copolymer used in the present invention comprises50 to 90 weight parts of at least one of styrene, α-methylstyrene, andnuclear substitution styrene; and 10 to 50 weight parts of at least oneof acrylonitrile, methylmethacrylate, and butylacrylate. The graftcopolymer resin can be prepared by a common polymerization method, butit is suitably synthesized by mass polymerization or emulsionpolymerization. The styrene-containing copolymer is used in an amount of30 to 70 weight parts of the total base resin according to the amount ofrubber-modified styrene-containing graft copolymer, thermoplasticpolyurethane, and phenol novolac resin.

(Flame-Retardant Aromatic or Aliphatic Phosphate)

As the aromatic or aliphatic phosphate used as a flame-retardant in thepresent invention, an aromatic or aliphatic monophosphate and anaromatic diphosphate can be used alone or in combination.

The aliphatic monophosphate includes a trialkylphosphate such astrimethylphosphate, triethylphosphate, tributylphosphate,trioctylphosphate, etc.; an aromatic monophosphate includes atriarylphosphate such as triphenylphosphate, tricresylphosphate,trixylylphosphate, crecyldiphenylphosphate, etc.; and atrialkylarylphosphate such as octyldiphenylphosphate, etc., which is notsubstituted with a halogen. Preferably, triarylphosphate is used, andmore preferably, triphenylphosphite, tri(4-methylphenyl)phosphate, ortri(2,6dimethylphenyl)phosphate is used.

In addition, the aromatic diphosphate is preferably a compound of thefollowing Chemical Formula 2 or pentaerythrityl diphosphate (PPP) of thefollowing Chemical Formula 3:

(wherein Ar₁˜Ar₄ is a phenyl group or an aryl group substituted with 1˜3C1-4 alkyl groups, R is phenyl or bisphenol A, and n is 4 or 5, showingdegree of polymerization.)

The aromatic monophosphate and aromatic diphosphate are preferably addedin an amount of 5 to 20 weight parts of 100 weight parts of the totalbase resin, alone or in combination. If the contents of theflame-retardant are less than 5 weight parts, flame-retarding propertiesdecrease, and if 20 weight parts are exceeded, the flame-retardingproperties are superior but processibility and other physical propertiessuch as impact strength decrease.

The composition of the present invention may further comprise anadditive selected from the group consisting of a lubricant, athermostabilizer, an antioxidant, a light stabilizer, an anti-drippingagent, a pigment, an inorganic filler, and a mixture thereof.

The flame-retarding styrenic thermoplastic resin composition of thepresent invention can be prepared by a common blending method.

The present invention will be explained in more detail with reference tothe following Examples. However, these are to illustrate the presentinvention and the present invention is not limited to them.

EXAMPLE

Preparation and specification of raw material used in Examples are asfollows:

(Rubber-Modified Styrene-Containing Graft Copolymer)

The rubber-modified styrene-containing graft copolymer resin is an LGChemical Inc. product, acrylonitrile/butadiene/styrene, which isprepared by grafting acrylonitrile and styrene on butadiene rubber,comprising 30 weight parts of styrene, 15 weight parts of acrylonitrile,and 50 weight parts of butadiene rubber, and which is synthesized byemulsion polymerization.

(Thermoplastic Polyurethane Resin)

The thermoplastic polyurethane resin is prepared by reacting adipicacid, glycol, and diisocyanate. Adipic acid and an excessive amount of amixture of ethylene glycol and polypropylene glycol are reacted toprepare polyester, which is reacted with diisocyanate to prepare acompound having a urethane structure. To 100 g of the compound, 1 g ofwater was added and heated, and the obtained solid powder is heated to150° C. under a pressure of 100 atm. to obtain thermoplasticpolyurethane resin.

(Phenol Novolac Resin)

Phenol novolac resin is prepared by synthesizing a compound of thestructure of the above Chemical Formula 1 wherein x is 0, an averagedegree of polymerization is 5, and a softening point is 130° C. Onemmole each of phenol and formalin are introduced into a reactor, and 1.5g of oxalic acid is added as a catalyst to cause reaction at 97° C., for12 hours. After reaction, the mixture is separated into resin and water.After removing the water, the pressure is reduced again, the resin isdehydrated by heating at 180° C. for 1 hour, and it is cooled to obtaina solid phenol novolac resin.

(Styrene-Containing Copolymer)

The styrene-containing copolymer comprises 70˜80 weight parts of styreneand 20˜30 weight pales of acrylonitrile, and is synthesized by emulsionpolymerization.

(Aromatic Phosphate)

As an aromatic monophosphate, triphenylphosphate (TPP) from JapanDaihachi Company was used. As an aromatic diphosphate, diphenylphosphate(PX-200) from Japan Daihachi Company and synthesized pentaerythrityldiphosphate (PPP) from LG Chemical, Ltd. were used.

Example 1

A flame-retarding thermoplastic resin was prepared with the compositionand contents as shown in Table 1. 10 weight parts of phenol novolacresin was blended with styrenic resin, and aromatic monophosphate, TPPwas used in an amount of 15 weight parts of 100 weight parts of thetotal resin as a flame-retardant.

Example 2

A flame-retarding thermoplastic resin composition was prepared with athe composition and contents as shown in Table 1 by the same method asin Example 1, except that aromatic diphosphate, PX-200 was used in anamount of 15 weight parts of 100 weight parts of the total base resin,instead of aromatic monophosphate, TPP as a flame-retardant.

Example 3

A flame-retarding thermoplastic resin composition was prepared with thecomposition and contents as shown in Table 1 by the same method as inExample 1, except that pentaerythrityl diphosphate, PPP was used in anamount of 15 weight parts of 100 weight parts of the total base resin,instead of aromatic monophosphate, TPP as a flame-retardant.

Example 4

A flame-retarding thermoplastic resin composition was prepared with thecomposition and contents as shown in Table 1 by the same method as inExample 1, except that aromatic monophosphate, TPP and aromaticdiphosphate, PX-200 were used respectively in an amount of 10 weightparts and 5 weight parts of 100 weight parts of the total base resin asa flame-retardant.

For the samples prepared in Examples 1˜4, the flame-retarding propertieswere measured according to the UL94 VB flammabilty test method, and theresults are shown in Table 1.

Evaluation Standard for Flame-Retarding Properties

SE: Self-extinguish, NR: No Rating

TABLE 1 Example 1 2 3 4 Base resin Rubber-modified styrene- ABS 35 35 3535 (weight containing graft copolymer parts) Phenol novolac resin 10 1010 10 Styrene-containing SAN 55 55 55 55 copolymer Flame- Aromaticmonophosphate TPP 10 — —  5 retardant Aromatic diphosphate PX-200 — 10 — 5 (Weight PPP — — 10 — part) Physical UL94 (⅛″) SE SE SE SE propertiesAverage combustion time (t1 + t2) 65 88 71 72

Example 5

As shown in Table 2, 20 weight parts of rubber-modifiedstyrene-containing graft copolymer, 10 weight parts of thermoplasticpolyurethane resin, and 10 weight parts of novolac resin were blendedwith 60 weight parts of styrene-containing copolymer, and aromaticmonophosphate, TPP was added thereto as a flame-retardant in an amountof 10 weight parts of 100 weight parts of the total resin to prepare aflame-retarding resin composition.

Example 6

A flame-retarding resin composition was prepared by the same method asin Example 5, except that the amount of aromatic monophosphate, TPP wasincreased to 15 weight parts of 100 weight parts of the total resin.

Example 7

A flame-retarding resin composition was prepared by the same method asin Example 5, except that as a flame-retardant, aromatic diphosphate,PX-200 was used in an amount of 15 weight parts of 100 weight parts ofthe total resin instead of aromatic monophosphate, TPP.

Example8

A flame-retarding resin composition was prepared by the same method asin Example 5, except that as a flame-retardant, aromatic diphosphate,PPP was used in an amount of 15 weight parts of 100 weight parts of thetotal resin instead of aromatic monophosphate, TPP.

Example 9

A flame-retarding resin composition was prepared by the same method asin Example 5, except that as a flame-retardant, on the basis of 100weight parts of total resin, 8 weight parts of aromatic monophosphate,TPP and 5 weight parts of aromatic diphosphate, PX-200 were used.

Example 10

A flame-retarding resin composition was prepared by the same method asin Example 5, except that among the total base resin, the amount ofthermoplastic polyurethane resin was decreased to 20 weight parts andthat of the styrene-containing copolymer was decreased to 50 weightparts; and as the flame-retardant, aromatic monophosphate, TPP was usedin an amount of 12 weight parts of the total resin.

Example 11

A flame-retarding resin composition was prepared by the same method asin Example 10, except that among the total base resin, the amount ofstyrene-containing graft copolymer was decreased to 25 weight parts andthat of the styrene-containing copolymer was decreased to 45 weightparts.

Example 12

A flame-retarding resin composition was prepared by the same method asin Example 10, except that among the total base resin, the amount ofthermoplastic polyurethane resin was increased to 30 weight parts andthat of the styrene-containing copolymer was decreased to 40 weightparts.

Table 2 shows the composition of Examples 5 to 12 and results ofmeasuring impact strength and flame-retarding properties of preparedsamples. Impact strength was measured as notched izod impact strengthaccording to ASTM D-256, and flame-retarding properties were measuredaccording to the UL94 VB flammability test standard.

TABLE 2 Examples 5 6 7 8 9 10 11 12 Base Rubber-modified ABS 20 20 20 2020 20 25 20 resin styrene-containing graft (weight copolymer parts)Polyurethane 10 10 10 10 10 20 20 30 Phenol novolac 10 10 10 10 10 10 1010 Styrene-containing SAN 60 60 60 60 60 50 45 40 copolymer Flame-Aromatic TPP 10 15 — —  8 12 12 12 retardant monophosphate (weightAromatic diphosphate PX-200 — — 15 —  5 — — — part) PPP — — — 15 — — — —Physical Impact strength (¼″) 22 19 18 17 20 23 26 28 properties UL94(⅛″) V-1 V-1 V-1 V-1 V-1 V-0 V-0 V-0

In Examples 5 to 9, when blending 10 weight parts of novolac resin and10 weight parts of thermoplastic polyurethane resin with the styrenecopolymer and using 10 weight parts or more of aromatic phosphate on thebasis of 100 weight parts of the total resin, compositions showed UL-94V-1. Also, although impact strength varied according to the kinds ofaromatic phosphate, the compositions showed the same flammability.

In addition, in Examples 10 to 12, when increasing the amount ofpolyurethane resin to 20 weight parts or more, the composition showed aflammability of UL-94 V-0, and when the rubber-modifiedstyrene-containing graft copolymer or thermoplastic polyurethane resinwas increased, the impact strength increased without change inflammability.

As explained, according to the present invention, a non-halogen styrenicthermoplastic flame-retarding resin composition having superiorflame-retarding properties and impact strength can be prepared by addingsmall amounts of novolac resin and thermoplastic polyurethane resin to arubber-modified styrenic resin.

1. A styrenic thermoplastic resin composition, without polycarbonate or polyphenylene ether, comprising a) 100 weight parts of a base resin, by weight of the base resin: i) 10 to 50 weight percent(wt. %) of a rubber-modified styrene-containing graft copolymer comprising 30 to 65 weight parts of a styrene compound and 10 to 30 weight parts of an acryl compound on 10 to 60 weight parts of a rubber, which the styrene compound is selected from the group consisting of a styrene, α-methylstyrene, nuclear substitution styrene, and a mixture thereof, and the acryl compound is selected from the group consisting of an acrylonitrile, methylmethacrylate, butylacrylate, and a mixture thereof, and the rubber is selected from the group consisting of polybutadiene, styrene-butadiene copolymer, polyisoprene, butadiene-isoprene copolymer, and a mixture thereof; ii) 5 to 20 wt. % of phenol novolac resin; iii) 30 to 70 wt. % of a styrene-containing copolymer comprising 50 to 90 wt % of a compound selected from the group consisting of styrene, α-methylstyrene, nuclear substitution styrene, and a mixture thereof and 10 to 50 wt % of a compound selected from the group consisting of acrylonitrile, methylmethacrylate, butylacrylate, and a mixture thereof; and iv) 10 to 40 wt. % of a thermoplastic polyurethane resin, and b) 5 to 20 weight parts of a phosphorous compound represented by the following Chemical Formula 3, which is not substituted with halogen:


2. The styrenic thermoplastic resin composition according to claim 1, wherein the thermoplastic polyurethane resin is prepared by polymer addition reacting a compound having two or more hydroxyl groups with a multifunctional isocyanate.
 3. The styrenic thermoplastic resin composition according to claim 1, wherein the phenol novolac resin is a compound represented by the following Chemical Formula 1:

wherein X is CH₂, CH₂CH₂, CHCH₃, CO, or SO₂; each of R is independently or simultaneously a hydrogen atom, a halogen atom, a C₁₋₂₀ alkyl group, an aryl group, NO₂, CN, Si, or a hydroxyl group; and n is an integer of 2 or more, showing degree of polymerization.
 4. The flame-retarding styrene thermoplastic resin composition according to claim 1, wherein the thermoplastic resin further comprises an additive selected from the group consisting of a lubricant, a thermo-stabilizer, an antioxidant, a light stabilizer, an anti-dripping agent, a pigment, an inorganic filler, and a mixture thereof.
 5. A styrenic thermoplastic resin composition, without polycarbonate, consisting essentially of: a) 100 weight parts of a base resin, by weight of the base resin: i) 10 to 50 weight percent(wt. %) of a rubber-modified styrene-containing graft copolymer comprising 30 to 65 weight parts of a styrene compound and 10 to 30 weight parts of an acryl compound on 10 to 60 weight parts of a rubber, which the styrene compound is selected from the group consisting of a styrene, α-methylstyrene, nuclear substitution styrene, and a mixture thereof, and the acryl compound is selected from the group consisting of an acrylonitrile, methylmethacrylate, butylacrylate, and a mixture thereof, and the rubber is selected from the group consisting of polybutadiene, styrene-butadiene copolymer, polyisoprene, butadiene-isoprene copolymer, and a mixture thereof; ii) 5 to 20 wt. % of phenol novolac resin; iii) 30 to 70 wt. % of a styrene-containing copolymer comprising 50 to 90 wt % of a compound selected from the group consisting of styrene, α-methylstyrene, nuclear substitution styrene, and a mixture thereof and 10 to 50 wt % of a compound selected from the group consisting of acrylonitrile, methylmethacrylate, butylacrylate, and a mixture thereof; and iv) 10 to 40 wt. % of a thermoplastic polyurethane resin, and b) 5 to 20 weight parts of a phosphorous compound represented by the following Chemical Formula 3, which is not substituted with halogen: 